Shadows skipping over streets in shadow study

[Anonymous]

I am trying to run a comparison of shadows between two hours of the day (12 and 1pm on Dec 21st). I have created a simple slab below all the buildings to represent the streets. The ArchiCAD seems to run the 12pm scenario just fine, with shadows falling on the streets adjacent to buildings as well as on buildings on neighboring blocks (see figure 1, attached). However, for some reason, in the 1pm scenario the shadows are not being cast on the streets (see figure 2).

The only change I’m making between the two is setting the hour ahead in the 3d projection settings from 12pm to 1pm. When I try it at other times of the year I get mixed results as well.

I am at a complete loss to understand what is going on. Is this a glitch in the software, or am I missing something?

Thanks for any advice you can offer.

- Josh